The present invention relates to a deflecting device in a two-valued charge type multi-nozzle ink jet printer.
In a two-valued charge type multi-nozzle ink jet printer, ink particles not used for printing (hereinafter referred to as "non-printing ink particles" when applicable) are charged so as to be deflected perpendicularly to the jet of ink particles by a deflecting device. The deflected particles are then recovered. On the other hand, ink particles used for printing are not charged and pass straightly through the deflecting device and strike the recording medium thereby to record a dot thereon.
In a conventional two-valued charge type ink jet printer, a high voltage is applied across the deflecting electrodes to create a deflecting electrodes field therebetween. The ink particles are injected into the electric field thus created and the non-printing ink particles are deflected perpendicularly to the direction of ink particles jet and are then recovered by a gutter.
The above-described conventional deflecting device suffers from the following difficulties:
(1) If dust particles from the ambient atmosphere have collected on the deflecting electrodes, an electrical discharge may occur between the deflecting electrodes or between the deflecting electrodes and other member at ground potential.
(2) Since a high voltage is applied thereto, the deflecting electrodes must be electrically insulated from conductors at ground potential. Thus, the structure and layout of the deflecting electrodes are limited making the manufacture of the device complex.
(3) Due to the presence of the high voltage, the distance between the deflecting electrodes and the recording medium must be large due to safety considerations. Therefore, the ink particles must fly through a relatively long distance to the recording medium.
(4) In a deflecting device for ink particles formed by nozzles positioned in a staggered arrangement, a deflecting electrode is provided between two ink particle lines and a high voltage is applied to the electrode to deflect the ink particles in opposite directions. Therefore, it is necessary to provide at least one deflecting electrode to which the high voltage is applied and two other deflecting electrodes at ground potential.